1. Field of the Invention
The present invention relates to a barrier device having a barrier member that can close an aperture in a portable digital camera or a camera unit mounted in a mobile phone or the like for protecting a lens or an ND filter when not in use. More particularly, the invention relates to a barrier device having a function to prevent penetration of dust, moisture or the like through a gap in the aperture area, which is provided for allowing movement of the barrier member.
2. Description of the Related Art
A known conventional barrier device includes a head cover defining a generally rectangular aperture for exposing a lens, a wall portion forming a retraction space on the backside of the head cover, a pair of barrier members disposed in the retraction space such as to be able to reciprocate within a plane orthogonal to an optical axis of the lens for closing the aperture when closed and opening the aperture when opened, and a dust/moisture protection member (seal member) shutting the retraction space along an upper and lower edge of the generally rectangular aperture (for example, see Japanese Unexamined Patent Publication No. 2005-173104).
This dust/moisture protection member is formed of a thin flexible material such as vinyl, rubber or the like. A torsion spring applies a force to keep it constantly biased such that it is pressed against the surface of the pair of barrier members when the barrier members close the aperture while it is pressed against the wall portion when the barrier members open the aperture.
However, this dust/moisture protection member is designed to shut the upper and lower edges of the substantially rectangular aperture, i.e., it does not shut the entire circumference of the aperture (including the left and right edges). There is thus a risk that dust, moisture or the like may penetrate through the left or right side of the aperture into the interior of the device.
Moreover, the dust/moisture protection member is constantly pressed against the surface of the pair of barrier members or the surface of the wall portion by a biasing force of the torsion spring. While the dust/moisture protection member has a linear shape, the pair of barrier members slides in a direction orthogonal to the dust/moisture protection member, because of which slide resistance is large when the pair of barrier members performs the open/close operation, and there is also a risk that the pair of barrier members may stick to the dust/moisture protection member and cannot perform the open/close operation smoothly.
Another problem is that since the dust/moisture protection member is formed of vinyl or rubber, it tends to aggravate the increase in the slide resistance and friction between the pair of barrier members and the dust/moisture protection member. Moreover, since the dust/moisture protection member is biased by the torsion spring, the structure is complex with a large number of components, which leads to a cost increase.